1. Field of the Invention
The invention relates generally to vehicular sensor systems. More specifically, the invention relates to an ultrasonic sensor system that filters unwanted signals from being reported by the system.
2. Background Art
Vehicular sensor systems are becoming increasingly popular as tools to increase driving safety, to avoid collisions with unseen objects, and to facilitate parking. As used herein, the terms “vehicle” and “vehicular” are used in their broadest sense, to encompass any means of motive transport.
An example of a prior art vehicular sensor system 100 is shown in FIG. 1. In this example, the vehicle is an automobile 102 having a sensor 104 mounted at a rear portion thereof. The sensor 104 emits ultrasonic pulses 106. If an object 108 is within detectable range of sensor 104, ultrasonic pulses are reflected by object 108 and returned as echo signals (not shown) to sensor 104. By knowing the speed of sound in air and the time for an ultrasonic pulse to travel to object 108 and an echo signal to return to sensor 104, the distance of the object to the sensor can be estimated. Accordingly, if an object is within a certain distance from automobile 102, a warning can be issued to the driver of automobile 102 to exercise due caution when reversing.
The detection range of a sensor may be shaped (i.e., expanded or contracted) depending upon different sources of noise surrounding a vehicle. For example, as a vehicle turns, the detection range of a sensor closest to the path of turning may be enlarged relative to other sensors to increase detection of objects likely to come into the path of the vehicle. Further, threshold values may be established for particular ranges of a sensor to increase or decrease the likelihood of detection of an object in those particular ranges.